Yeah my buddy has a 3/4 ton Avalanche with the "monster towing motor" 6.0L IIRC. Tows like crap. My 1/2 ton tows better than his Avalanche does, no exaggeration. I towed the same size camper with my truck, on the same route, big difference.
He has had every power window motor swapped out in it twice, the instrument cluster went out on it a couple of times, his has always had brake issues and had the master cylinder go on it. Im not sure if the truck has 100k on it yet.
I wouldnt touch one with a 10 foot pole, especially one that has been sitting around like that one. You know why it has new tires, right? They dry rotted from sitting. You can expect the same from other things as well.
JMO